1. Field of the Invention
This invention relates in general to drop balls, plugs, or darts used to operate running tool functions and, in particular, to a universal launcher for launching a drop ball, plug, or dart into a running string.
2. Brief Description of Related Art
Standard dart or ball launchers have a member that defines a central bore that may be coupled inline with a drill or tubing string. The launchers also include an angular bore that intersects the central bore at a shallow angle between the angular bore and the central bore. A dart or ball is dropped into the angular bore, and after opening a series of valves, the ball or dart is introduced into the central bore for further movement of the dart or ball down the borehole. There, the dart or ball will land at a predetermined location to block the borehole and allow hydraulic tool operations. In order to minimize the potential that the ball will snag or hang up as it moves from the angular bore to the central bore, the angle of the intersection between the two axes is as close to zero degrees as possible. This necessitates that the launcher must be very tall to smooth out the transition between the angular bore and the central bore. The height can make the launcher very difficult to access and operate. Despite incredibly shallow angles, many times the dart or ball hangs up or snags where the angular bore meets the central bore; this prevents operation of the downhole tool, and necessitates that the launcher be broken out and reset for further operations down the tubing or drill string.
Other devices couple inline with the drill or tubing string and use a series of valves to launch the ball or dart. Again, the dart or ball may become stuck or snagged at the valve openings, preventing successful operation of the dart or drop ball. In addition, these types of devices require bypass passages within the valves so that fluids may flow around the darts and valves prior to launching the dart or ball. These passages restrict fluid flow through the running string and may become clogged. Clogging of these passages will, in turn, require stoppage of drilling operations in order to remove and reset the launcher for operation. Even when not blocked, these passages may restrict the flow of fluid down hole, causing further complications in drilling operations. Thus, there is a need for a launcher that launches the dart or ball from an inline coupling without restricting fluid flow through the central bore of the tubing.